I was doing some unrelated testing and was looking at what mods I had that altered armor meshes. This is one of the mods I've had installed for a long time. I'm not sure if it's been forgotten, but I figured I'd give it a bump and include a few screenshots I took for comparison.

I feel that this mod vastly improves the appearance of the glass helmet, particularly on male characters. On males you can actually see through the helmet on either side of the characters head. The fit for the female helmets isn't nearly as bad, and from what I can tell, this mod only slightly narrows the top of the female helmet.

To address torminater's concern about the beast races, they use different meshes which (unfortunately) aren't altered by this mod.

Here are my comparisons. I apologize for just linking to the folder, but for some reason when I tried to insert individual image links, they were showing up as broken. The files are named in a way which should hopefully make it clear which are vanilla and which are from this mod.

I think the only difference between them is that Glass Helmet Fix includes an esp that changes the armor addon record so that the elven ears don't clip (an issue present in the vanilla meshes as well as the "better fitting" meshes). The screenshots I took are still valid for Better Fitting Glass Helmet, with the exception of the side shots. These would show the tip of the ear clipping through the helmet (similar to the vanilla shot) if it weren't for the addition of the Glass Helmet Fix edits.

Yep, I realized a few minutes after posting that I'm not using the original mod, but actually using Glass Helmet Fix (then, of course, my internet connection died and I couldn't get my post updated right away). :P